This invention relates to a method of producing foam-filled stud walls, and to apparatus for implementing the method.
It has long been known that a foam-filled wall is very desirable from an insulation (i.e. heat transfer) viewpoint, and various methods have been used in the past to produce such walls.
No suitable method or apparatus has yet been developed to facilitate rapid and efficient prefabrication of such walls on an assembly-line basis. The present invention is directed towards providing a suitable assembly line method and apparatus for implementing the method for producing prefabricated foam-filled walls.
The type of wall intended to be filled is the type commonly used in wood frame construction, i.e. a wall having a base plate, a top plate, window and door openings, and a number of spaced vertical studs, the plates and studs most commonly being either nominal two-by-four or two-by-six lumber. However, this invention is not limited either to specific stud sizes or spacings, nor to any specific stud material.
In the prior art, urethane insulation has been applied on site to standing stud walls, typically by spraying a spray-type foam onto the wall and building up an insulating layer roughly an inch at a time. As spray-type foams are highly exothermic, the layers of insulation must be built up gradually. This type of system is generally cumbersome, messy, and may produce an uneven surface with no certainty that all voids, including corner cavities, are filled.
Another attempted solution in the prior art has been to inject measured amounts of foam between panels, but this is difficult or impossible to do in the case of prefabricated stud walls, especially when dealing with varying wall sizes. Injecting an incorrect amount of foam may result either in voids in the insulation, or in the wall being forced apart by the expanding foam. The latter problem may possibly be avoided by utilizing a full press on both sides of the wall, but in addition to requiring more elaborate equipment, this also means that non-standard wall sizes cannot be readily accommodated, nor can window openings and the like.
In the prior art, various types of equipment have been used for injecting foam into double-membrane panels, such as those found in metal garage doors, for example. Such systems suffer from a number of serious drawbacks which prevent or severely restrict their applicability to stud walls. These drawbacks include the fact that a complete filling may not take place, and may not even be possible, if the panel includes window and door openings. Another serious problem with this type of system is that, since both front and rear panels must be in place to contain the foam, either a finished interior surface, or a superfluous interior panel (to be covered later by a finished surface), must be provided. If a finished interior surface such as gypsum board or "drywall" is installed at the plant location, further handling of the panel is made far more difficult. This type of panel would not only weigh more, but would need to be handled with great care in order to avoid damaging the finished surface.
A method for producing a prefabricated insulated wall panel is disclosed in U.S. Pat. No. 4,409,768 granted to Boden in October 1983. The preferred embodiment of this invention employs multiple dams to contain the foam introduced into a wall. The patent also discloses the use of a single dam to cover the area to be filled. Boden does not, however, introduce a half-completed stud wall into an apparatus comprising a backplate and a moveable dam. He rather lays his stud wall onto a backplate and then lays a series of plates upon the stud wall. There is thus no point at which the stud wall is inserted between a dam and a backplate. Boden does also not contemplate the moving of a single dam along a stud wall progressively as the foam sets. He is more likely to use a single plate which covers the entire area to be filled.
A method for insulating walls is disclosed in U.S. Pat. No. 4,093,411, granted to Lee in June 1978. Lee teaches a process for covering a surface with foam. Lee does not introduce a wall between a backplate and a dam, but rather translates his machine along a surface. Moreover, he does not advance a dam towards the bottom portion of the open side of the stud wall to a predetermined distance from the backplate. This movement of the dam ensures that, if the studs are warped or vary in width, they will be forced back into contact with the front surface of the sheathing backplate to ensure that the foam does not escape between the rear surface of the stud and the backplate, and uniformity of the front of the studs to ensure that the foam does not exude between the dam and the studs.
Lee discloses an apparatus having a continuous or endless belt, and does not suggest the use of a single plate moved along the stud wall in discrete steps with a delay between such steps to allow for setting of the foam. It should be noted that although Lee shows a pressure plate behind the belt, it merely serves to limit the expansion of the foam, and has no means for urging it into contact with underlying studs so as to straighten any misalignment or to adjust for varying thickness.
It is highly desirable to have a method and apparatus which permits the filling not only of uniform size wall sections without window openings or the like, but also the filling of varying sizes of wall sections with varying sizes and locations of window openings. It is also highly desirable to have a method and apparatus which permits the filling of walls without requiring the presence of any interior panel, finished or otherwise.